Vacuum wound therapy wound dressing with variable performance zones

ABSTRACT

A dressing for an open wound includes a cover layer dimensioned for positioning relative to a wound bed. The cover layer permits an evacuation of the space around the wound bed such that a sub-atmospheric pressure may be established to stimulate healing and facilitate the removal of fluid from the wound. Multiple performance zones in the cover layer allow the wound dressing to remain in position through repeated cycles of evacuation without placing undue strain on the wound bed. An outer peripheral zone may include a high peal-strength adhesive while an intermediate zone may include a shear resistant adhesive. A central zone may be devoid of any coating to maximize moisture transmission through cover layer.

BACKGROUND 1. Technical Field

The present disclosure relates generally to a wound dressing fortreating an open wound with a vacuum wound therapy treatment. Inparticular, the disclosure relates to a dressing having a cover layeremploying a plurality of zones of variable performance characteristicsto promote healing of the wound.

2. Background of Related Art

The body's natural wound healing process is a complex series of eventsbeginning at the moment of injury. Initially the body reacts bydelivering proteins and other factors to the wound through the bloodstream to minimize the damage. Blood clots to prevent blood loss whilecells engulf bacteria and debris to carry it away from the wound site.Next, the body begins to repair itself in a stage of healing oftenreferred to as the proliferate phase. This phase is characterized by thedeposition granulation tissue in the wound bed. Granulation tissueprovides a base structure over which cells may migrate inwardly from theperiphery to close the wound. Finally the process ends as collagen givesstrength to new tissue over time often forming a scar.

One technique for promoting the natural healing process, particularly,but not exclusively during the proliferate phase, is known as vacuumwound therapy (VWT). Application of a reduced pressure, e.g.sub-atmospheric, to a localized reservoir over a wound has been found toassist in closing the wound. The reduced pressure may be effective topromote blood flow to the area to stimulate the formation of granulationtissue and the migration of healthy tissue over the wound in the naturalprocess. Also a reduced pressure may assist in removing fluids exudingfrom the wound, which may inhibit bacterial growth. This technique hasproven effective for chronic or non-healing wounds, but has also beenused in for other purposes such as post-operative wound care.

The general VWT protocol provides for the introduction of a fillermaterial into the wound to absorb exudates. The filler material maycomprise such materials as non-reticulated foams, non-woven fabrics orgauze. The wound and the filler material may then covered by moisturevapor permeable cover layer that permits oxygen exchange with theenvironment, which may be essential for wound healing. The cover layeroften includes an adhesive periphery that forms a substantially fluidtight seal with the healthy skin surrounding the wound. The cover layerthus defines a vacuum reservoir over the wound where a reduced pressuremay be maintained over time by individual or cyclic evacuationprocedures.

An aspect of concern in a VWT treatment is the management of forcesgenerated in the dressing when a vacuum is applied. Such forces maycause the separation of the dressing from the skin, thereby limiting theeffect of the VWT treatment and increasing the probability thatmicroorganisms will infect the wound. Also, such forces may damage newlyforming granulation tissue. The application of a vacuum can deform aflexible cover layer such that it compresses the filler and increasesits tendency to adhere to the wound bed. Additionally, the deformationof the cover layer creates transverse shear forces along theskin-adhesive interface at the peri-wound area. These shear forces cancause the dressing to shift and/or pull away from the skin where gapsand wrinkles may develop. Such movement, and the mentioned resultsthereof, can inhibit the dressing's ability to provide a seal that issuitable for both the maintenance of a vacuum and for prohibiting theinfiltration of contamination.

Adhesives applied to a cover layer to strengthen or reinforce thedressing's attachment to the skin may diminish the moisture vaporpermeability of the dressing affecting its ability to permit oxygenexchange with the environment. Diminished moisture vapor permeabilitycould also lead to the accumulation of moisture at the skin-adhesiveinterface. Permitting such an accumulation undermines the dressing'sadhesion to the skin at the peri-wound area, thereby reducing thewear-time of the dressing, the effectiveness of the treatment and thehealth of the peri-wound area. Accordingly a need exists for a dressingsuitable for use in a VWT procedure.

SUMMARY

The present disclosure describes a dressing for use in a vacuum woundtherapy procedure to promote healing of a wound. The dressing includes acover layer having a plurality of zones of variable performancecharacteristics. A central zone is defined by a portion of a moisturevapor permeable membrane devoid of any coating that would otherwiseinhibit the transmission of moisture through the membrane. A peripheralzone adjacent a periphery of the cover layer is adapted to provide aseal around the perimeter of the wound. At least one intermediate zoneis disposed between the central zone and the peripheral zone to impart atherapeutic effect or benefit to the wound.

The peripheral zone may include a high peal-strength adhesive while afirst intermediate zone may include a shear-resistant adhesive. A secondintermediate zone may include a coating adapted for medicament delivery,a hydrogel for maintaining a moist wound environment, or at least one ofan anti-infective agent, an antimicrobial, antibiotic, analgesic,healing factor, vitamins, growth factors, debridement agents ornutrients.

The moisture variable permeable membrane may extend to a periphery ofthe cover layer so as to constitute a backing layer for the attachmentof an adhesive defining the peripheral zone. The peripheral zone and atleast one intermediate zone may be arranged concentrically with respectto the central zone. The cover layer may also include a port forpermitting access to a vacuum reservoir defined beneath the cover layerfor a vacuum tube.

According to another aspect of the disclosure a wound dressing apparatusfor use in a vacuum wound therapy procedure includes a contact layer anda filler material positioned in a wound bed and covered by a coverlayer. The cover layer defines a vacuum reservoir above the wound bedand permits access of a vacuum tube to the vacuum reservoir. The coverlayer includes a peripheral zone to provide a seal around the wound bed,at least one intermediate zone for imparting a therapeutic effect orbenefit to the wound bed, and a central zone formed from a moisturevapor permeable membrane.

The contact layer may be formed from a conical apertured film to promoteunidirectional flow of exudates from the wound. The absorbent fillermaterial may include polyolefin filaments arranged in a multi-strandbundle. Also, a vacuum system in fluid communication with the vacuumreservoir may include a vacuum source, a collection canister and aone-way valve.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate embodiments of the presentdisclosure and, together with the detailed description of theembodiments given below, serve to explain the principles of thedisclosure.

FIG. 1 is an exploded perspective view of a vacuum wound therapy systemin accordance with the present disclosure;

FIG. 2A is a perspective view of the vacuum wound therapy system of FIG.1 assembled for use on a patient;

FIGS. 2B and 2C depict alternate assemblies of the vacuum wound therapysystem;

FIG. 3A is a reverse angle perspective view of the cover layer of FIG.1;

FIG. 3B depicts an alternate embodiment of the cover layer;

FIG. 4A is a cross sectional view of the vacuum wound therapy system ofFIG. 1 in a first condition exhibiting a vacuum reservoir; and

FIG. 4B depicts the vacuum wound therapy system in a second conditionwherein the vacuum reservoir is evacuated.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The wound dressing of the present disclosure promotes healing of a woundby providing a reservoir over the wound where a reduced pressure may bemaintained. The reservoir subjects the wound to a sub-atmosphericpressure to effectively draw wound fluid, including liquid exudates,from the wound without the continuous use of a vacuum pump. Hence,vacuum pressure may be applied once, or in varying intervals dependingon the nature and severity of the wound. The use of a wound dressing inthis manner has been found to promote healing by reducing theprobability of infection, stimulating the deposition of granulationtissue and other beneficial processes. The wound dressing of the presentdisclosure includes a cover layer having multiple performance zones toenhance the effect of a vacuum wound therapy treatment.

The attached figures illustrate exemplary embodiments of the presentdisclosure and are referenced to describe the embodiments depictedtherein. Hereinafter, the disclosure will be described in detail byexplaining the figures wherein like reference numerals represent likeparts throughout the several views.

Referring initially to FIG. 1, a vacuum wound therapy system accordingto the present disclosure is depicted generally as 10 for use on a wound“w” surrounded by healthy skin “s.” The vacuum wound therapy system 10includes a vacuum system 12 in fluid communication with a vacuumreservoir 14 (FIG. 4A) defined by or within the wound dressing 16. Thevacuum system 12 includes a vacuum source 18 coupled to the dressing 16through a one-way valve 20 and a vacuum tube 24. A collection canister28 is provided for wound drainage and debris. The vacuum system 12 isadapted to provide a reduced pressure to the vacuum reservoir 14appropriate to stimulate healing of the wound. A more detaileddescription of an appropriate vacuum system 12 is found in commonlyassigned U.S. Patent Application Publication 2007/0066946, the entirecontents of which are incorporated herein by reference.

Wound dressing 16 generally includes a contact layer 34, filler 38 and acover layer 40 defining a plurality of performance zones. A backinglayer 44 may be coated with various materials in a juxtaposed relationto define a peripheral zone 48, a first intermediate zone 52, a secondintermediate zone 56 and a central zone 58 (FIG. 3A). Alternatively,each zone may comprise an independent layer positioned adjacent thewound bed “w.” Each layer is described in greater detail below.

Contact layer 34 may be sufficiently conformable to be positioned indirect contact with an irregularly shaped surface of a wound bed “w.” Athin film of polyethylene or other suitable non-adherent material mayform the contact layer 34 to limit the adherence of filler 38 and othersubstances to the wound “w.” Apertures or perforations in the filmpermit fluids to pass through the contact layer 34, allowing for thesub-atmospheric pressure to penetrate into the wound “w” and forexudates to flow freely out of the wound “w.” By selecting anappropriate film material, the passage of wound exudate through contactlayer 34 may be controlled so as to be substantially unidirectional toprevent wound exudate from flowing back into the wound. To promote aunidirectional flow, a conical apertured film, such as those provided byTredegar Film Products of Richmond, Va., may be selected for formingcontact layer 20. This type of film is arranged with aperturespositioned at the peaks of cone shaped formations in the film materialsuch that exudate encounters the film as an array of micro-funnels inone direction and an array of collecting basins in the other.Unidirectional flow of exudates may also be promoted by the selection ofother materials including a lamination of layers having varyingabsorptive characteristics. One exemplary material, which may be used asa contact layer is sold under the trademark XEROFLO® by Kendall Corp., adivision of Covidien.

Filler 38 may be arranged over contact layer 34 to fill wound “W” to thelevel of the surrounding healthy skin “s,” or alternatively the wound“w” may be overfilled with filler 38. An absorbent material such asnon-woven gauze or reticulated foam may be used for filler 38 to trapany exudate that migrates through contact layer 34. An antimicrobialdressing sold under the trademark KERLIX™ AMD™ by Kendall Corp., adivision of Covidien, may be suitable for use as filler 38. To preventadhesion to the wound “w,” the filler 38 may also comprise a materialconfigured such that its fibers do not tend to protrude throughapertures of contact layer 34 where they may become engulfed by newlyforming granulation tissue. One particular type of material exhibitingthis characteristic is often referred to as “tow.” The manufacturingprocess for synthetic fibers often includes an extrusion of anindeterminate length of continuous filaments, which are spun together toform fibers. Continuous lengths of un-spun filaments may be arranged inmulti-strand bundles which are referred to as tow. A single length oftow formed from a hydrophobic material such as polyolefin may be laid inthe wound bed “w” to form filler 38. This arrangement allows for acomplete removal of filler 50 when the dressing 16 is changed withoutre-injuring the wound “w.”

Cover layer 40 may be placed over the wound “W” enclosing the contactlayer and filler therein. The periphery of cover layer 40 extendslaterally beyond the perimeter of the wound bed “w” so as to contact thehealthy skin “s” to form a seal over the wound “w.” As depicted in FIG.2A, an opening 60 may be provided or formed through the cover layer 40to provide access for the vacuum tube 44 to communicate with the vacuumreservoir 14, or the vacuum tube 44 may be sealed under the periphery ofthe cover layer 40 as depicted in FIG. 2B. Alternatively, a distinctportal member or port 62 may be provided to facilitate fluidcommunication between the vacuum system 12 and the vacuum reservoir 14as depicted in FIG. 2C. Port 62 may be configured as a rigid or semirigid, low-profile component adapted to receive the vacuum tube 24 in areleasable and fluid-tight manner. The vacuum port 62 may be configuredto include a wide and flexible flange 64 about its perimeter. The flange64 permits an adhesive to be attached to either an underside of flange64 for securement to an outer surface of cover layer 40, or to a topside of flange 64 to provide for mounting to the underside of the coverlayer 40.

Referring now to FIG. 3A, cover layer 40 includes multiple performancezones 48, 52, 56 and 58 comprising various materials. A backing layer 44may extend to the periphery of the cover layer 40 to provide a substratefor various coatings or materials defining the various performance zones48, 52, 56 and 58. As depicted, each of the performance zones 48, 52, 56and 58 is a continuous band arranged concentrically with respect to theothers. The size, shape and position of the zones, however, may bevaried according to the needs of the particular wound or treatment. Forexample, a cover layer 40A as depicted in FIG. 3B may be providedcomprising a first intermediate zone 52 formed from a pattern ofdistinct shapes surrounded by second intermediate zone 56A. The variouscoatings may be laminated to the backing layer 44 or affixed by otherappropriate means. The various materials forming layer 40 are describedin greater detail herein below.

Backing layer 44 may be formed from a flexible polymeric membrane to actas a fluid barrier to allow for a sub-atmospheric pressure to beestablished in vacuum reservoir 14. The material's flexibilityaccommodates the pressure changes associated with the evacuation cyclesin a VWT procedure. Backing layer 44 also serves as a microbial barrierpreventing contaminants from entering the wound area. Preferably, thebacking layer 44 is formed from a moisture vapor permeable membrane topromote the exchange of oxygen and moisture between the wound site andthe atmosphere. A membrane that provides a sufficient moisture vaportransmission rate (MVTR) and is simultaneously impervious to liquid maybe selected for use as backing layer 44. Another preferred membranecharacteristic is the ability to stretch and conform to the compressedwound filler or wound bed. A membrane's tendency for elongation whensubjected to a vacuum reduces the shear forces transitioned to theperi-wound area. One exemplary material for use in backing layer 44 is atransparent membrane sold under the trade name DURAFLEX® by DeerfieldUrethan, a Bayer Material Science Company. Other materials which may besuitable for use in a backing layer include the thin films marketedunder the names POLYSKIN®II by Kendall Corp., a division of Covidien,TEGADERM™ by 3M of St. Paul, Minn. and OPSITE™ by Smith and Nephew PLCof London, UK. A central zone 58 of the cover layer is defined by thearea of the backing layer 44 not covered with any material which wouldtend to lessen the MVTR.

At the periphery of the cover layer 40 is a peripheral zone 48 definedby a continuous layer of high peal-strength, pressure sensitiveadhesive. The adhesive forms a seal with the skin “s” around theperimeter of the cover layer to prevent the ingress of atmosphericfluids under the edges of the cover layer 40 when a reduced pressure isestablished in the reservoir 14. The adhesive defining the peripheralzone 48 is adapted to prevent the loss of adhesion to the skin even whenexposed to environmental factors such as exudates from the wound “w” orbody movements by the patient. In general, the high peal-strengthadhesive is adapted to resist inadvertent lift-off, roll or “flagging,”i.e., a failure of the dressing to adhere to itself, at the edges of thecover layer. The adhesive defining the peripheral zone 48 may include,for example, those adhesives included with the dressing sold under thetrademark GELVA® Multipolymer Solutions by CYTEC Surface SpecialtiesInc.

The high peal-strength adhesive defining peripheral zone 48 may bebonded to backing layer 44, or applied directly to the skin “s”surrounding the wound bed “w.” The adhesive should preferably benon-irritating and non-sensitizing to the contacted skin, and may bevapor moisture permeable to permit the contacted skin to transmitmoisture. Preferably, the peripheral zone 48 and first intermediate zone52 are positioned so as not to overlap the contact layer 34 as seen inFIGS. 4A and 4B. This arrangement facilitates the changing of certainindividual components of the dressing, such as filler 38 withoutremoving the entire dressing 16.

Disposed between the peripheral zone 48 and central zone 58 are firstand second intermediate zones 52 and 56 respectively. First and secondintermediate zones 52, 56 are defined by a layer of a substance forimparting a therapeutic effect or benefit to the wound “w.” As indicatedabove, first and second intermediate zones 52, 56 may be arranged ascontinuous bands concentric with central zone 58 as seen in FIG. 3A, asa pattern of distinct shapes as seen in FIG. 3B, or any other convenientarrangement.

First intermediate zone 52 may, for example, be defined by a layer of anadhesive that laterally stabilizes the dressing when a reduced pressureis applied to evacuate the reservoir. As seen in FIG. 4B, when thereservoir is evacuated, the cover layer may tend to flatten against thewound “w.” This may result in an outwardly directed force in thedressing 16 which may tend to separate the cover layer 40 from the skin“s.” Also, the shear forces in the cover layer 40 may be transmitted tothe skin “s,” pulling apart newly forming granulation tissue andre-injuring the wound “w.” To counteract these tendencies, ashear-resistant adhesive may be selected for use in first intermediatezone 52. Since many high peal-strength adhesives are adapted primarilyto resist upwardly directed forces, i.e., those forces tending to liftthe cover layer from the skin, a high peal-strength adhesive definingthe peripheral zone 48 may be supplemented with an adhesive particularlyadapted to resist lateral forces defining the first intermediate zone52. A shear-resistant adhesive, such as GMS 1753 manufactured by CYTECSurface Specialties Inc., that is moisture vapor permeable and suitablefor use on the skin, may be used to define first intermediate zone 52.

Second intermediate zone 56 may be defined by a layer of a distinctmaterial for providing a therapeutic effect or benefit to the wound. Forexample, second intermediate zone 56 may be adapted for transdermalmedicament delivery. A substance such as an anti-infective agent, anantimicrobial, antibiotic, analgesic, healing factor, vitamins, growthfactors, debridement agents or nutrients may be coated on portions ofbacking layer 108 to define second intermediate zone 56. Alternatively,a hydrogel may be selected for use in second intermediate zone 56 tomaintain a moist wound environment. As seen in FIG. 4B, secondintermediate zone 56 may be in contact with filler 38 when the reservoir14 is evacuated to permit transfer beneficial agents thereto. Filler 38and contact layer 34 may be eliminated if appropriate allowing forsecond intermediate zone 56 to contact the wound bed directly. It isalso contemplated that an additional attachment adhesive may bebeneficial for use in second intermediate zone 56.

Although the foregoing disclosure has been described in some detail byway of illustration and example, for purposes of clarity orunderstanding, it will be obvious that certain changes and modificationsmay be practiced within the scope of the appended claims.

1.-14. (canceled)
 15. A wound dressing for use with a negative pressurewound therapy apparatus, the wound dressing comprising: a cover layercomprising a continuous band of adhesive material on a periphery of thecover layer; and a wound contact layer configured to be positioned incontact with a wound, the wound contact layer comprising a peripheralregion, wherein the continuous band of adhesive material of the coverlayer is adhered to the peripheral region of the wound contact layer,and wherein the continuous band of adhesive material extends beyond theperipheral region of the wound contact layer and is configured to form aseal with skin surrounding the wound; wherein the continuous band ofadhesive material comprises a first adhesive configured to form a sealwith the skin surrounding the wound; and wherein a second adhesive isprovided on a surface that is surrounded by the first adhesive; whereinthe first adhesive is different from the second adhesive.
 16. The wounddressing of claim 15, wherein the first adhesive comprises a highpeel-strength adhesive.
 17. The wound dressing of claim 15, furthercomprising a fluid flow passage configured to be in fluidiccommunication with a source of negative pressure.
 18. The wound dressingof claim 17, wherein the fluid flow passage is configured to permit aone way flow of fluid away from the wound dressing when negativepressure is applied to the wound dressing.
 19. The wound dressing ofclaim 17, wherein the fluid flow passage comprises a one way valve. 20.The wound dressing of claim 17, further comprising a port configured tobe in fluid communication with the source of negative pressure, whereinthe port is configured to permit attachment of the fluid flow passage.21. The wound dressing of claim 20, wherein the port comprises a flangeabout its perimeter.
 22. The wound dressing of claim 21, wherein theflange comprises an adhesive on an underside of the flange forsecurement to an outer surface of the wound dressing.
 23. The wounddressing of claim 15, further comprising a filler configured to absorbwound exudate within the wound dressing.
 24. The wound dressing of claim23, wherein the filler comprises polyolefin filaments arranged in amulti-strand bundle.
 25. The wound dressing of claim 23, wherein thefiller comprises an absorbent material.
 26. The wound dressing of claim23, wherein the filler comprises a non-woven gauze or reticulated foam.27. The wound dressing of claim 15, further comprising a negativepressure source in fluid communication with the wound dressing, whereinthe negative pressure source is configured to apply negative pressure tothe wound dressing.
 28. The wound dressing of claim 15, wherein thecover layer comprises a central zone comprising a moisture vaporpermeable membrane.
 29. The wound dressing of claim 15, wherein thesecond adhesive is provided on the cover layer.